Variable volume combustor with an air bypass system

ABSTRACT

The present application provides a combustor for use with flow of fuel and a flow of air in a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles positioned within a liner and an air bypass system position about the liner. The air bypass system variably allows a bypass portion of the flow of air to bypass the micro-mixer fuel nozzles.

STATEMENT RETARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract No. DE-FC26-05NT42643 awarded by the U.S. Department of Energy. The Government has certain rights in this invention.

TECHNICAL FIELD

The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to a variable volume combustor with an air bypass system for improved turndown performance.

BACKGROUND OF THE INVENTION

Operational efficiency and the overall output of a gas turbine engine generally increases as the temperature of the hot combustion gas stream increases. High combustion gas stream temperatures, however, may produce higher levels of nitrogen oxides and other types of regulated emissions. A balancing act thus exists between the benefits of operating the gas turbine engine in an efficient high temperature range while also ensuring that the output of nitrogen oxides and other types of regulated emissions remain below mandated levels. Moreover, varying load levels, varying ambient conditions, and many other types of operational parameters also may have a significant impact on overall gas turbine efficiency and emissions.

Lower emission levels of nitrogen oxides and the like may be promoted by providing for good mixing of the fuel stream and the air stream prior to combustion. Such premixing tends to reduce combustion temperature gradients and the output of nitrogen oxides. One method of providing such good mixing is through the use of a combustor with a number of micro-mixer fuel nozzles. Generally described, a micro-mixer fuel nozzle mixes small volumes of the fuel and the air in a number of micro-mixer tubes within a plenum before combustion.

Although current micro-mixer combustors and micro-mixer fuel nozzle designs provide improved combustion performance, the operability window for a micro-mixer fuel nozzle in certain types of operating conditions may be defined at least partially by concerns with dynamics and emissions. Specifically, the operating frequencies of certain internal components may couple so as to create a high or a low frequency dynamics field. Such a dynamics field may have a negative impact on the physical properties of the combustor components as well as the downstream turbine components. Given such, current combustor designs may attempt to avoid such operating conditions by staging the flows of fuel or air to prevent the formation of a dynamics field. Staging seeks to create local zones of stable combustion even if the bulk conditions may place the design outside of typical operating limits in terms of emissions, flammability, and the like. Such staging, however, may require time intensive calibration and also may require operation at less than optimum levels.

There is thus a desire for improved micro-mixer combustor designs. Such improved micro-mixer combustor designs may promote good mixing of the flows of fuel and air therein so as to operate at higher temperatures and efficiency but with lower overall emissions and lower dynamics. Moreover, such improved micro-mixer combustor designs may accomplish these goals without greatly increasing overall system complexity and costs.

SUMMARY OF THE INVENTION

The present application and the resultant patent thus provide a combustor for use with flow of fuel and a flow of air in a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles positioned within a liner and an air bypass system positioned about the liner. The air bypass system variably allows a bypass portion of the flow of air to bypass the micro-mixer fuel nozzles.

The present application and the resultant patent further provide a method of turning down a combustor for use with a flow of fuel and a flow of air in a gas turbine engine. The method may include the steps of positioning a number of micro-mixer fuel nozzles within a liner, positioning a number of air bypass holes through the liner, maneuvering the micro-mixer fuel nozzles to open the air bypass holes in the liner, flowing a bypass portion of the flow of air away from the micro-mixer fuel nozzles, and reducing the flow of fuel to the micro-mixer fuel nozzles.

The present application and the resultant patent further provide an air bypass system for use with a flow of fuel and a flow of air in combustor. The air bypass system may include a number of micro-mixer fuel nozzles positioned within a cap assembly, the cap assembly positioned within a liner, and a number of air bypass holes positioned about the liner. The air bypass holes allow a bypass portion of the flow of air to bypass the micro-mixer fuel nozzles.

These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic diagram of a gas turbine engine showing a compressor, a combustor, and a turbine.

FIG. 2 is a schematic diagram of a combustor that may be used with the gas turbine engine of FIG. 1.

FIG. 3 is a schematic diagram of a portion of a micro-mixer fuel nozzle that may be used with the combustor of FIG. 2.

FIG. 4 is a schematic diagram of a micro-mixer combustor as may be described herein.

FIG. 5 is a perspective view of an example of the micro-mixer combustor of FIG. 4.

FIG. 6 is a side cross-sectional view of the micro-mixer combustor of FIG. 5.

FIG. 7 is an expanded view of a portion of a nested fuel manifold system as may be used with the micro-mixer combustor of FIG. 5.

FIG. 8 is a schematic view of the air bypass system as used with the micro-mixer combustor of FIG. 5 in a closed position.

FIG. 9 is a further schematic view of the air bypass system of FIG. 8 in an opened position.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIG. 1 shows a schematic view of gas turbine engine 10 as may be used herein. The gas turbine engine 10 may include a compressor 15. The compressor 15 compresses an incoming flow of air 20. The compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor 25 mixes the compressed flow of air 20 with a pressurized flow of fuel 30 and ignites the mixture to create a flow of combustion gases 35. Although only a single combustor 25 is shown, the gas turbine engine 10 may include any number of the combustors 25. The flow of combustion gases 35 is in turn delivered to a turbine 40. The flow of combustion gases 35 drives the turbine 40 so as to produce mechanical work. The mechanical work produced in the turbine 40 drives the compressor 15 via a shaft 45 and an external load 50 such as an electrical generator and the like.

The gas turbine engine 10 may use natural gas, liquid fuels, various types of syngas, and/or other types of fuels and combinations thereof. The gas turbine engine 10 may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine 10 may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together.

FIG. 2 shows a schematic diagram of an example of the combustor 25 as may be used with the gas turbine engine 10 described above and the like. The combustor 25 may extend from an end cover 52 at a head end to a transition piece 54 at an aft end about the turbine 40. A number of fuel nozzles 56 may be positioned about the end cover 52. A liner 58 may extend from the fuel nozzles 56 towards the transition piece 54 and may define a combustion zone 60 therein. The liner 58 may be surrounded by a flow sleeve 62. The liner 58 and the flow sleeve 62 may define a flow path 64 therebetween for the flow of air 20 from the compressor 15 or otherwise. Any number of the combustors 25 may be used herein in a can-annular array and the like. The combustor 25 described herein is for the purpose of example only. Combustors with other components and other configurations may be used herein.

FIG. 3 shows a portion of a micro-mixer fuel nozzle 66 that may be used with the combustor 25 and the like. The micro-mixer fuel nozzle 66 may include a number of micro-mixer tubes 68 positioned about a fuel tube 70. The micro-mixer tubes 68 generally may have substantially uniform diameters and may be arranged in annular, concentric rows. Any number of the micro-mixer tubes 68 may be used herein in any size, shape, or configuration. The micro-mixer tubes 68 may be in communication with the flow of fuel 30 from the fuel tube 70 via a fuel plate 72 and the flow of air 20 from the compressor 15 via the flow path 64. A small volume of the flow of fuel 30 and a small volume of the flow of air 20 may mix within each micro-mixer tube 68. The mixed fuel-air streams may flow downstream for combustion in the combustion zone 60 and used in the turbine 40 as described above. Other components and other configurations may be used herein.

FIG. 4 shows an example of a combustor 100 as may be described herein. The combustor 100 may be a micro-mixer combustor 110 with any number of the micro-mixer fuel nozzles 120 and the like positioned therein. The micro-mixer fuel nozzles 120 may be similar to those described above. The micro-mixer fuel nozzles 120 may be sector shaped, circular shaped, and/or have any size, shape, or configuration. Likewise, the micro-mixer nozzles 120 may include any number of micro-mixer tubes therein in any configuration. The micro-mixer fuel nozzles 120 may be in communication with a common fuel tube 125. The common fuel tube 125 may carry one or more fuel circuits therein. The multiple fuel circuits thus may allow staging of the micro-mixer fuel nozzles 120. The micro-mixer fuel nozzles 120 may be mounted within a cap assembly 130 or a similar structure. The cap assembly 130 may have any size, shape, or configuration. The cap assembly 130 may be surrounded by a conventional seal 135 and the like.

Similar to that described above, the combustor 100 may extend from an end cover 140 at a head end 150 thereof A liner 160 may surround the cap assembly 130 and the seal 135 with the micro-mixer fuel nozzles 120 therein. The liner 160 may define a combustion zone 170 downstream of the cap assembly 130. The liner 160 may be surrounded by a case 180. The liner 160, the case 180, and a flow sleeve (not shown) may define a flow path 190 therebetween for the flow of air 20 from the compressor 15 or otherwise. The liner 160, the combustion zone 170, the case 180, and the flow path 190 may have any size, shape, or configuration. Any number of the combustors 100 may be used herein in a can-annular array and the like. Other components and other configurations also may be used herein.

The combustor 100 also may be a variable volume combustor 195. As such, the variable volume combustor 195 may include a linear actuator 200. The linear actuator 200 may be positioned about the end cover 140 and outside thereof The linear actuator 200 may be of conventional design and may provide linear or axial motion. The linear actuator 200 may be operated mechanically, electro-mechanically, piezeo-electrically, pneumatically, hydraulically, and/or combinations thereof By way of example, the linear actuator 200 may include a hydraulic cylinder, a rack and pinion system, a ball screw, a hand crank, or any type of device capable of providing controlled axial motion. The linear actuator 200 may be in communication with the overall gas turbine controls for dynamic operation based upon system feedback and the like.

The linear actuator 200 may be in communication with the common fuel tube 125 via a drive rod 210 and the like. The drive rod 210 may have any size, shape, or configuration. The common fuel tube 125 may be positioned about the drive rod 210 for movement therewith. The linear actuator 200, the drive rod 210, and the common fuel tube 125 thus may axially maneuver the cap assembly 130 with the micro-mixer nozzles 120 therein along the length of the liner 160 in any suitable position. The multiple fuel circuits within the common fuel tube 125 may allow for fuel nozzle staging. Other components and other configurations also may be used herein.

In use, the linear actuator 200 may maneuver the cap assembly 130 so as to vary the volume of the head end 150 with respect to the volume of the liner 160. The liner volume (as well as the volume of the combustion zone 170) thus may be reduced or increased by extending or retracting the micro-mixer fuel nozzles 120 along the liner 160. Moreover, the cap assembly 130 may be maneuvered without changing the overall system pressure drop. Typical combustor systems may change the overall pressure drop. Such a pressure drop, however, generally has an impact on cooling the components therein. Moreover, variations in the pressure drop may create difficulties in controlling combustion dynamics.

Changing the upstream and downstream volumes may result in varying the overall reaction residence times and, hence, varying the overall emission levels of nitrogen oxides, carbon monoxide, and other types of emissions. Generally described, reaction residence time directly correlates to liner volume and thus may be adjusted herein to meet the emission requirements for a given mode of operation. Moreover, varying the residence times also may have an impact on turndown and combustor dynamics in that overall acoustic behavior may vary as the head end and the liner volumes vary.

For example, a short residence time generally may be required to ensure low nitrogen oxides levels at base load. Conversely, a longer residence time may be required to reduce carbon monoxide levels at low load conditions. The combustor 100 described herein thus provides optimized emissions and dynamics mitigation as a tunable combustor with no variation in the overall system pressure drop. Specifically, the combustor 100 provides the ability to vary actively the volumes herein so as to tune the combustor 100 to provide a minimal dynamic response without impacting on fuel staging.

Although the linear actuator 200 described herein is shown as maneuvering the micro-mixer fuel nozzles 120 in the cap assembly 130 as a group, multiple linear actuators 200 also may be used so as to maneuver individually the micro-mixer fuel nozzles 120 and to provide nozzle staging. In this example, the individual micro-mixer fuel nozzles 120 may provide additional sealing therebetween and with respect to the cap assembly 130. Rotational movement also may be used herein. Moreover, non-micro-mixer fuel nozzles also may be used herein and/or non-micro-mixer fuel nozzles and micro-mixer fuel nozzles may be used together herein. Other types of axial movement devices also may be used herein. Other component and other configurations may be used herein.

FIG. 5 and FIG. 6 show an example of a pre-nozzle fuel injection system 220 that may be used with the combustor 100 and the like. Each of the fuel nozzles 120 may be mounted onto the pre-nozzle fuel injection system 220. The pre-nozzle fuel injection system 220 may include a fuel nozzle manifold 230. The fuel nozzle manifold 230 may be in communication with the common fuel tube 125 and may be maneuverable via the drive rod 210 as described above. The fuel nozzle manifold 230 may have any size, shape, or configuration.

The fuel nozzle manifold 230 of the pre-nozzle fuel injection system 220 may include a center hub 240. The center hub 240 may have any size, shape, or configuration. The center hub 240 may accommodate a number of different flows therein. The fuel nozzle manifold 230 of the pre-nozzle fuel injection system 220 may include number of support struts 250 extending from the center hub 240. Any number of the support struts 250 may be used. The support struts 250 may have a substantially aerodynamically contoured shape 255 although any size, shape, or configuration may be used herein. Specifically, each of the support struts 250 may include an upstream end 260, a downstream end 270, a first sidewall 280, and a second sidewall 290. The support struts 250 may extend radially from the center hub 240 to the cap assembly 130. Each support strut 250 may be in communication with one or more of the fuel nozzles 120 so as to provide the flow of fuel 30 thereto. The fuel nozzles 120 may extend axially from the downstream end 270 of each of the support struts 250. Other components and other configurations may be used herein.

FIG. 7 shows a nested fuel manifold system 320 as may be described herein. The nested fuel manifold system 320 may cooperate with the pre-nozzle fuel injection system 220 or other type of fuel injection system so as to deliver safely one or more flows of fuel 30 to the fuel nozzles 120. Moreover, the nested fuel manifold system 320 also may cooperate with the linear actuator 200 and the drive rod 210 to accommodate the axial movement of the fuel nozzles 120 within the cap assembly 130 while limiting the number of penetrations through the end cover 140.

The nested fuel manifold system 320 includes a nested fuel manifold 330. The nested fuel manifold 330 may be positioned about the linear actuator 200 outside of the end cover 140 at the head end 150 for movement therewith. The nested fuel manifold 330 may include a number of fuel circuit connections 340. Any number of the fuel circuit connections 340 may be used. The fuel circuit connections 340 may be in communication with the same or different types of flows of fuel 30 so as to provide fuel flexibility herein. The fuel circuit connections 340 may have any size, shape, or configuration.

Each of the fuel circuit connections 340 of the nested fuel manifold 330 may be in communication with a nested fuel supply circuit 350. In this example, three (3) nested fuel supply circuits 350 are shown: a first nested fuel supply circuit 360, a second nested fuel supply circuit 370, and a third nested fuel supply circuit 380. Any number of the nested fuel supply circuits 350, however, may be used herein. The nested fuel supply circuits 350 may be annularly nested within each other such that the first nested fuel supply circuit 360 is positioned within the second nested fuel supply circuit 370 which, in turn, is positioned within the third nested fuel supply circuit 380. A fuel feed seal 390 may separate each of the nested fuel supply circuits 350. Each of the nested fuel supply circuits 350 may take the form of a flexible hose and the like. The nested fuel supply circuits 350 may have any size, shape, or configuration. The nested fuel supply circuits 350 collectively act as the common fuel tube 125. Other components and other configurations may be used herein.

FIGS. 8 and 9 show an example of an air bypass system 800 that may be used with the combustor 100 and the like. The air bypass system 800 may include a number of air bypass holes 810 positioned through the liner 160. The air bypass holes 810 may be positioned through the liner 160 about an aft end 820 of the cap assembly 130. The air bypass holes 810 may be positioned in a single row 830 or a number of rows 830 may be axially arranged so as to provide staging. The air bypass holes 810 may have any size, shape, or configuration. Air bypass holes 810 of different sizes, shapes, and configurations may be used together herein in any orientation. Any number of the air bypass holes 810 may be used herein. Other components and other configurations may be used herein.

In this example, the seal 135 on the cap assembly 130 may be in the form of a hula seal 840 and the like. Generally defined, the hula seal 840 may be a finger seal or a leaf spring used to seal a sliding interface or an annular gap between two concentric ducts. Other types of seals 135 and sealing mechanism may be used herein. Any number of the hula seals 840 may be used herein in any size, shape, or configuration. The hula seals 840 may be positioned about the aft end 820 of the cap assembly 130. Such positioning avoids potential damage to a thermal barrier coating 850 and the like on the hot surface of the liner 160. Other components and other configurations may be used herein.

FIG. 8 shows the air bypass system 800 in a closed position 860. Specifically, when the cap assembly 130 is advanced in a downstream direction within the liner 160, the hula seals 840 prevent the flow of air 20 therethrough. FIG. 9 shows the air bypass system in an open position 870. In this position, the hula seals 840 are upstream of the air bypass holes 810 when the cap assembly 130 is retracted to a full aft position 880. The full aft position 880 provides the largest combustor volume and, hence, the longest residence time. With the air bypass holes 810 open, a bypass portion 890 of the flow of air 20 may flow therethrough and bypass the fuel nozzles 120. The air bypass holes 810 may be configured to allow a predetermined volume of the bypass portion 890 to flow therethrough.

The use of the bypass portion 890 of the flow of air 20 allows for less of the flow of fuel 30 to be provided to the fuel nozzles 120. The air bypass system 800 thus allows for the combustor 100 to be turned down to a much lower point while maintaining the same fuel to air ratio to the fuel nozzles 120 for stable flame performance. Moreover, the air bypass system 800 may improve overall emissions compliance by dumping the bypass portion 890 away from the center nozzle so as to control the formation of carbon monoxide. The hula seals 840 also may be positioned such that only a predetermined number of the bypass holes 810 may be open so as to vary the volume of the bypass portion 890 and, hence, so as to vary the fuel to air ratio to the fuel nozzles 120. The air bypass system 800 may precisely control the volume of the bypass portion 890 by varying the position of the hula seals 840 and the cap assembly 130 via the linear actuator 200. The air bypass system 800 thus may have any number of partially open positions with the hula seals 840 upstream of some of the air bypass holes 810.

The air bypass system 800 thus provides the combustor 100 with improved turn down performance without the use of addition components for an overall robust system. The air bypass system 800 allows for further turndown, emissions compliance, and dynamics mitigation. The combustor 100 thus may operate within required parameters at relatively low loads.

It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof. 

We claim:
 1. A combustor for use with a flow of fuel and a flow of air in a gas turbine engine, comprising: a plurality of micro-mixer fuel nozzles, wherein the plurality of micro-mixer fuel nozzles is positioned within a cap assembly, wherein the assembly is positioned within a liner; a seal positioned between the cap assembly and the liner; an air bypass system positioned about the liner, wherein the air bypass system comprises: a plurality of air bypass holes through the liner, an open position when the cap assembly is advanced in a downstream direction such that the seal is maneuvered downstream of the plurality of air bypass holes to prevent the flow of air therethrough, and a closed position when the cap assembly is retracted in an upstream direction such that the seal is maneuvered upstream of the plurality of air bypass holes to enable a bypass portion of the flow of air to bypass the plurality of micro-mixer fuel nozzles.
 2. The combustor of claim 1, wherein the plurality of micro-mixer fuel nozzles comprises a plurality of micro-mixer fuel tubes and a fuel plate.
 3. The combustor of claim 1, wherein the plurality of air bypass holes is configured in a row.
 4. The combustor of claim 1, wherein the plurality of air bypass holes is configured in a plurality of rows.
 5. The combustor of claim 1, wherein the seal is positioned about an aft end of the cap assembly.
 6. The combustor of claim 1, wherein the open position comprises the cap assembly in a full aft position.
 7. The combustor of claim 1, wherein the air bypass system comprises a partially opened position with the seal partially upstream of the air bypass system.
 8. The combustor of claim 1, wherein the seal comprises a hula seal.
 9. The combustor of claim 1, further comprising a linear actuator to maneuver the plurality of micro-mixer fuel nozzles within the liner.
 10. A method of turning down a combustor for use with a flow of fuel and a flow of air in a gas turbine engine, comprising: positioning a plurality of micro-mixer fuel nozzles within a liner; positioning a plurality of air bypass holes through the liner; maneuvering a seal positioned about the plurality of micro-mixer fuel nozzles to open the air bypass holes in the liner; flowing a bypass portion of the flow of air away from the plurality of micro-mixer fuel nozzles; and reducing the flow of fuel to the plurality of micro-mixer fuel nozzles. 